The present invention relates generally to electric powered trip units, such as circuit breakers and more particularly to a communication and control system that cooperates with the electronic trip units.
In a typical factory-power distribution system, power is generated by a power generation company and supplied to a factory and thereafter distributed around the factory to various equipment such as, for example, motors, welding machinery, computers, heaters, lighting, and the like.
Power distribution systems of this type are typically centrally located in switch gear rooms or substations. From there, power is divided up into branches such that each branch supplies power to a portion of the factory and/or specified loads. Frequently, transformers are disposed throughout the factory to step down the supply voltage to that required by specific pieces of equipment or portions of the factory. Therefore, a factory-power distribution system typically has a number of transformers servicing various types of equipment in various areas. Inherent with this, is the high cost of the power-distribution equipment such as transformers, as well as the cost of the equipment to which power is being supplied. Therefore, it is quite common to provide protective devices such as circuit breakers or fuses in at least each branch so that not only may each piece of equipment be protected but any problems associated with one piece of equipment does not ripple to adjacent or interconnected pieces of equipment. Further, providing fuses or circuit breakers in each branch can help minimize down time since specific loads may be energized or de-energized without affecting other loads thereby creating increased efficiencies, lower operating and manufacturing costs and the like.
Typically, when circuit breakers are utilized, they are used to detect more than just large overcurrent conditions caused by short circuit faults. In addition, they frequently detect lower level long-time overcurrent conditions and excessive ground currents. The simplest form of circuit breakers are thermally tripped as a result of heating caused by overcurrent conditions and, in this regard, are basically mechanical in nature. These mechanical-type breakers are incorporated into almost all circuit breakers, regardless of whether or not additional advanced circuitry is provided since they are extremely reliable over a long life cycle and provide a default trip-type level of protection.
Some types of circuit breakers utilize electronic circuitry to monitor the level of current passing through the branch circuits and to trip the breaker when the current exceeds a pre-defined maximum value. Electronic circuit breakers are adjustable so as to fit a particular load or condition by the end user without designing or specifying different breakers. Breakers of this type typically include a microcontroller coupled to one or more current sensors. The microcontroller continuously monitors the digitized current values using a curve which defines permissible time frames in which both low-level and high-level overcurrent conditions may exist. If an overcurrent condition has maintained for longer than its permissible time frame, the breaker is tripped.
Microcontrolled breakers may also include the ability to calculate root mean square (RMS) current values. This is necessary in order to prevent erroneously tripping a circuit breaker when a non-linear load, such as a welding machine, is coupled to the branch that it is protecting. The reason for this is that nonlinear loads tend to produce harmonics in the current waveform. These harmonics tend to distort the current waveform, causing it to exhibit peak values which are augmented at the harmonic frequencies. When the microcontroller, which assumes that the current waveform is a sinusoidal current waveform, detects these peaks it may therefore trip the breaker even though the heating effect of the distorted waveform may not require that the circuit be broken.
Further, microcontrollers in some circuit breakers are used to monitor and control or account for other types of faults, such as over or under voltage conditions and phase loss or imbalances. Such microcontrollers operate solenoids which are operatively connected to the trip mechanism of the circuit breaker. Therefore, while the thermal overload (mechanical) portion of the breaker will operate the trip mechanism, the solenoid will operate at the instruction of the microcontroller (or sometimes also at the instruction of external signals) to allow the trip mechanism to trip the associated circuit breaker.
Further, as a result of the flexibility and breadth of protection that microcontrollers can provide when used in conjunction with circuit breakers, their use in circuit breakers is becoming more and more prevalent to the point of being standard. However, this presents another problem in that microcontrollers and the associated circuitry require power. Such power may be typically provided in one of three ways or a combination thereof and would utilized either batteries, externally-supplied power, or power provided by potential transformers. Most users provide one power supply having battery back-up, for supplying all of the controllers for the entire substation or switch gear closet.
Moreover, the monitoring of power characteristics is being demanded more and more frequently in load control equipment and particularly in Molded Case Circuit Breakers (MCCB) as is frequently found in use in industry. Such power components include, RMS and peak voltage, current and power, either by phase or in total and power factor related components. Utilities and industrial customers are increasingly interested in performing end-use load studies. These studies are typically in the form of collecting interval power data so as to monitor and control energy consumption. While this is often done at a main load center, due to the increased costs and problems associated with time of use power consumption, such monitoring is being done closer to the individual end-use loads (i.e., motors, etc.). In this fashion, industrial customers are given a financial incentive to curtail power consumption when the cost of power is high as well as being able to more carefully and cost-effectively manage their power consumption by knowing where in their plant significant amounts of energy are being used.
When power monitoring is to be done, a discrete energy transducer is installed on the equipment or circuit to be monitored. This transducer generates a digital pulse output via a mechanical or solid state relay with the frequency of the pulse output being proportional to the magnitude of the measured quantity. This digital pulse output is either hard wired or communicated via power line-carrier system to a discrete pulse data recording device where it is time stamped.
Because of the flexibility and configurability of microprocessor controlled circuit breakers and the large size and complexity of the industrial settings in which they are used, there is a need for a centralized system providing communications to and from the circuit breakers. Also, there is a need for a communication system providing reconfigurability of the circuit breakers from a centralized location. Further, there is a need for monitoring of circuit breakers at a centralized location. Further still, there is a need for a circuit breaker system that can communicate with a central system, the central system providing monitoring, communication and control functions from a central location to the circuit breaker system.
One embodiment of the invention relates to an information system. The information system includes a circuit breaker connectable to a load and having a current interrupting portion. The information system also includes a data processing unit and a communications bus configured to be coupled to the data processing unit. The information system further includes an electronic monitoring unit, configured to provide at least one of monitoring, control, and communications functions for the circuit breaker and the electronic monitoring unit in communication with the circuit breaker and with the communications bus.
Another embodiment of the present invention relates to a circuit breaker communications, monitoring, and control system. The circuit breaker communications, monitoring, and control system includes a central data processing unit and a communications bus coupled to the central data processing unit. The system also includes an application specific module coupled to the communications bus and a circuit breaker connectable to a load and having a current interrupting portion, and the circuit breaker coupled to the application specific module and communicating electronic signals with the application specific module.
Still another embodiment of the invention relates to a circuit breaker system configured for use in a commercial environment. The circuit breaker system includes a circuit breaker connectable to a load and having a current interrupting portion. The system also includes a data processing means and a communications bus configured to be coupled to the data processing means. The system further includes an interfacing means, configured to provide at least one of monitoring, control, and communications functions for the circuit breaker and the electronic monitoring unit in communication with the circuit breaker and with the communications bus.